From 2006 to 2010

Building Regulations, Part L

Can a building designed to a 15% better standard than the 2006 Building Regulations be improved to comply with 2010 regulations. Buro Happold’s David Kingstone took up the challenge.

Scarcely, it seems, have designers of buildings and their services installations got fully conversant with the requirements of the 2006 Building Regulations than they are faced with the even more demanding requirements of the 2010 regulations.

Expectations that full-height glazing would no longer be specified by architects for their creations and that architects would no longer regard making buildings comply with Part L of the regulations as the task of the M&E consultant have not been fulfilled in practice. Perhaps it is fortunate that Building Control has seldom enforced the regulations.

What happened instead is that manufacturers improved the efficiency of their products so that technical fixes could provide solutions at a fairly low cost. The principal easy wins were lighting and heat recovery.

It seems unlikely that such a step change in improvements can be achieved again, especially with the substantial increase in CO2 emissions for electricity, up almost 20% from about 420 to around 510 g/kWh. Emissions from primary fuels have also increased marginally. There has been a small decrease in emissions for wood pellets and even a halving for wood chips, but emissions for these fuels were already about a tenth those of oil, LPG and natural gas.

The nature of the task of making the transition from Part L of 2006 to Part L of 2010 is indicated by a case study carried out by David Kingstone of Buro Happold, and presented at a recent CIBSE conference.

He took as his starting point a new speculative office in Manchester designed to Part L 2006 and then considered a series of improvements to reduce its CO2 emissions to the level required by the 2010 regulations.

This multi-storey building with a 35 x 25 m office floor plate was designed with active chilled beams, rooftop boilers and air-cooled chillers, rooftop DHW calorifiers and office lighting with daylight and occupancy control.

As the Fig. 1 shows, this building had no difficulty complying with the 2006 Building Regulations — by a margin of 15%.

In a little more detail, the boilers had a seasonal efficiency of 86%, and the air-cooled chillers a good seasonal energy-efficiency rating of 4.2. The specific fan power of the ventilation plant was a relatively poor 3.1 W/l/s, but this was largely due to only a small riser duct being provided. The office lighting had a design power consumption of 3.0 W/m2/100 lx. Finally the curtain walling had a U-value of 0.95 W/m2/K and the windows 1.8 W/m2/K.

CO2 emissions for the notional building were 47 kg/m2 of CO2 a year and for the target building 28% less at 34 kg/m2. The actual design came in at 29 kg/m2 — 15% below the target and a sizable 38% below the notional building.

The 2010 regulations define no fewer than 23 types of notional building, and CO2 emissions for this particular building are 39% lower than the 2006 regulations. As Fig. 2 shows, the successful 2006 design fails by a substantial margin. The task is to reduce emissions by 21% .

David Kingstone’s initial approach on this hypothetical project was to see what reductions in CO2 emissions could be made without bringing in renewable energy.

Building Regulations, Part L
Fig. 1 (Left): The modelled building had CO2 emissions 15% below the 2006 target. This chart is based on the Part L 2006 methodology with boilers having a seasonal efficiency of 86%, air-cooled chillers having a seasonal EER of 4.2, specific fan power for fresh air of 3.1 W/l/s, office lighting at 3.0 W/m2/100 lx and the curtain wall having a U value of 0.95 /1.8 W/m2K. Fig. 2 (Right): When compared with the 2010 Building Regulations the modelled building is substantially above the target CO2 emissions.

The first stage was to improve the lighting efficiency to the level set in the notional building.

The next stage was to reduce the specific fan power by enlarging the cross-section of the air-handling units and the riser ducts.

Improvements in the building fabric then followed, but not of the glazing and roof as they were already very good.

The use of energy alarms give an automatic 5% credit which is also applied to the notional building.

The final stage was to improve the seasonal boiler efficiency from 86 to 89%; it had little effect on the outcome since heating energy consumption for this type of building is small.

All those incremental improvements still led to the building exceeding its TER (target energy rating) by 4.5%. Further improvements such as achieving duct and air-handling-unit air-tightness standards could have been considered prior to resorting to low- and-zero carbon technologies.

Combined cycle combined heat and power (CCHP) was next plugged into the calculation, and eventually achieved a building just 0.6% below the TER.

An alternative to CCHP was to consider a biomass boiler, but this is not as beneficial as it might seem as the TER is tightened up from 21 to 18 kg/m2 of CO2 a year. Even so, the building with a biomass boiler comes in at about 17.5 kg/m2 (Fig. 3) — 4.2% below the TER.

From that detailed examination of incremental improvements to the M&E services, David Kingstone concludes that compliance without renewables would have been difficult.

The experiment prompted David Kingstone to suggest that a better starting point would be to look at the building fabric rather than just the M&E plant and systems. In particular, he suggested that attention to facade engineering would have helped optimise the energy used for lighting, heating and cooling. Evaluation of the implications of the new methodology is, of course, ongoing.

This exercise required extremely good performance from the M&E plant to achieve 2010 compliance, and it is unlikely that much further improvement can be expected.

Building Regulations, Part L
Fig. 3: Whereas specifying a biomass boiler has enabled our building to comply with the 2010 Building Regulations, the TER has also been tightened up.
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